Question: What is in the category described by source of Mardonius ?
SPARQL (Wikidata): select distinct ?answer where { wd:Q155063 wdt:P1343 ?answer}
Answer: Brockhaus and Efron Encyclopedic Dictionary, Ottův slovník naučný, Small Brockhaus and Efron Encyclopedic Dictionary, Real'nyj slovar' klassicheskih drevnostej po Ljubkeru